docs: def _read_lineage_csv(file, comments):
          """ Read and parse CSV file generated by lineage.
  
          Parameters
          ----------
          file : str
              path to file
          comments : str
              comments at beginning of file
  
          Returns
          -------
          pandas.DataFrame
              individual's genetic data normalized for use with `lineage`
          str
              name of data source(s)
          """
          source = ""
          for comment in comments.split("\n"):
              if "Source(s):" in comment:
                  source = comment.split("Source(s):")[1].strip()
                  break
  
          df = pd.read_csv(
              file,
              comment="#",
              header=0,
              na_values="--",
              names=["rsid", "chrom", "pos", "genotype"],
              index_col=0,
              dtype={"chrom": object, "pos": np.int64},
          )
  
          return sort_snps(df), source